"A country that cannot feed itself, fuel itself or defend itself has few options," Canadian Prime Minister Mark Carney said at the World Economic Forum in Davos, where he pledged Canada stands "firmly" with Denmark against the territorial claims.

Belgian Foreign Minister Maxime Prévot went further, characterizing the U.S. approach as "incomprehensible and unnecessarily hostile." He warned that territorial seizure constitutes "a red line for European countries" and suggested the European Union may deploy its "anti-coercion instrument"—a trade retaliation mechanism—if diplomatic efforts fail.

Britain, France, and Germany have dispatched military delegations to Greenland in a show of solidarity, while NATO faces an existential question: what happens when the alliance's most powerful member threatens to invade the territory of another member state?

Historical parallels are disquieting. The last time Washington seized territory from a European power was in 1898, when it took Puerto Rico, Guam, and the Philippines from Spain. The last time a major Western power annexed European-controlled territory through military threat was Russia's seizure of Crimea in 2014—an action that resulted in comprehensive international sanctions.

European leaders are now confronting the reality that those historical categories may no longer apply in an era when the American president views allied sovereignty as negotiable. For the residents of Greenland, wearing their defiant red caps in sub-zero temperatures, the abstract geopolitical crisis has become uncomfortably concrete.